Abstract
Night-time measurements of the Earth’s undisturbed, quiet magnetic field at satellite altitudes provide models of the main field and its secular variation, and of the crustal magnetic anomaly field. Fields from the regular daily variations of solar and lunar origin are most pronounced in daytime data and can affect aeromagnetic and ground magnetic surveys. Satellite magnetic data in total intensity are now available across all local times, and for the first time it is possible to determine the regular daily variations in the ionosphere-magnetosphere region. We give the daily variation in total intensity at satellite altitudes for six equally spaced Universal Time epochs each covering daytime and night-time, showing clearly the equatorial electrojet and Sq current system above the ionosphere during daytime hours. Also given are crustal magnetic anomaly maps, based on high-degree residuals in main field data, for the world and the Australian region at satellite altitudes. The daily variations and crustal magnetic anomalies at satellite levels are both of the order of 20 nT.
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